Turbine blades in power units are made of alloys based on Ti, Ni or Co, and an aluminide layer is formed on the blades to protect them against corrosion by hot gases. The aluminide layer is removable in a process disclosed in U.S. Pat. No. 4,339,282. A disadvantage of the process in this patent and of the etch solution which is disclosed therein is that they cannot be used for protective metallic layers based on MCrAlY wherein M is a metal such as Co, Ni or Ta. These layers are characterized by their higher resistance to the corrosive attack of hot gases and to deposits deriving from hot gas reactions. However, the removal of such layers with known etch solutions for the removal of aluminide layers is not possible without considerable etching into, and removal of the material of the turbine blade. The composition of known etch solutions is based on a high proportion of pure acids such as nitric acid, fluoric acid, hydrochloric acid, sulfuric acid or mixtures of these together with small additions of salts, such as iron chloride or copper sulfate, and inhibitors which are intended to reduce etching into the material of the turbine blade.